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Abstract In this paper, the fatigue life of rolling lobe air springs made from cord-rubber composites is investigated with particular focus on the crack nucleation approach. Commonly used test specimens like the simple tension test specimen or the dumbbell specimen fail in the fatigue analysis of rolling lobe air springs because the fatigue characteristic of the cord-rubber interface is represented insufficiently. Therefore a new cord-rubber specimen is developed. The fatigue characteristic of the new specimen is discussed and Wöhler curves for two different predictors based on Cauchy stress and configurational stress are determined. Using FEA with a two-scale model of the air spring, the cycles-to-failure with respect to piston diameter and different inner pressures are determined and compared to test results taken from the literature. The results from the literature were derived at elevated temperature. Therefore, the Arrhenius approach is used to take into account different temperatures. In addition the crack growth approach using the cracking energy density is applied. The results show an improvement in the prediction of rolling lobe air springs fatigue life with respect to the crack initiation plane orientation and the cycles-to-failure using the new specimen. Compared to the crack nucleation approach, the crack growth approach seems to slightly overpredict the fatigue lives. Highlights • A new cord-rubber-composite specimen is developed to characterize the fatigue behaviour of the cord-rubber-interface, to use the results in the crack nucleation approach. • For the application of the crack nucleation approach, the local values of the predictors have to be determined. Therefore a two-scale approach for the finite element analysis is adapted. • The failure mechanisms in the cord-rubber-composite are determined and distinguished with the help of micro CT scans. • The predicted air spring lifetimes are in good agreement with the values from the literature. The influence on the lifetime for different inner pressures, rolling piston diameters and environmental temperatures are discussed in the paper. [ABSTRACT FROM AUTHOR]

Background Laboratory tests, electrocardiogram ( ECG) and chest X-rays still serve as part of the routine assessment before elective surgery in many institutions, even though there is little evidence of their predictive value relating to perioperative complications. This study investigates the correlation of abnormal findings in pre-operative tests and pathologic findings in the medical history with perioperative complications. Methods Patients scheduled for elective surgery in a secondary care hospital were included in this prospective cohort study. Abnormal pre-operative tests, significant findings from the medical history and perioperative complications were recorded. Regression analysis was performed in order to identify the strongest predictors for perioperative complications. Results A total of 1363 (56.1% female) patients were consecutively included in this study. The percentage of abnormalities in pre-operative tests ranged from 1.6% (electrolytes) and 29.7% (echocardiography). Eighty-six (6.3%) patients had at least one perioperative complication. The most frequent complications were hypo- or hypertension in 55 cases (4.0%), followed by 20 patients (1.5%) who suffered from hemodynamically relevant cardiac dysrhythmias such as supraventricular tachycardia, ventricular tachycardia, bradycardia and ventricular extrasystoles. The binary logistic regression analysis to identify predictors of perioperative complications showed significant results for age, invasiveness of the procedure, history of renal disease or anemia and abnormal ECG. Conclusion Our results indicate that age, type of surgery and medical history are appropriate predictors of perioperative complications, whereas abnormalities in laboratory tests seem to have restricted ability in predicting adverse perioperative outcome. [ABSTRACT FROM AUTHOR]

Abstract: This article provides detailed investigations into the fatigue behavior of natural rubber. Very important aspects of this, like Mullins-effects, strain crystallization, crack nucleation at flaws and crack growth, are examined in detail and used to explain experimental results. In addition to SEM micrograph investigations of the fracture surfaces, new aspects of fatigue fracture of rubber can be explained and well-known explanations can be confirmed. It is shown, that the global crack growth in the direction of the crack front is caused by interactions of several cracks growing in alternating directions. Results from strain-controlled experiments show that Woehler curves also are valid in regions of very high loads. Further experiments, using a spectrum of two different amplitudes each, clarify that Miner’s rule also is valid for damage accumulation when the load spectrum contains few excessively high loads. [Copyright &y& Elsevier]

Elective surgery is usually preceded by preoperative diagnostics to minimize risk. The results are assumed to elicit preventive measures or even cancellation of surgery. Moreover, physicians perform preoperative tests as a baseline to detect subsequent changes. This systematic review aims to explore whether preoperative testing leads to changes in management or reduces perioperative mortality or morbidity in unselected patients undergoing elective, non-cardiac surgery. We systematically searched all relevant databases from January 2001 to February 2011 for studies investigating the relationship between preoperative diagnostics and perioperative outcome. Our methodology was based on the manual of the Ludwig Boltzmann Institute for Health Technology Assessment, the Scottish Intercollegiate Guidelines Network (SIGN) handbook, and the PRISMA statement for reporting systematic reviews. One hundred and one of the 25 281 publications retrieved met our inclusion criteria. Three test grid studies used a randomized controlled design and 98 studies used an observational design. The test grid studies show that in cataract surgery and ambulatory surgery, there are no significant differences between patients with indicated preoperative testing and no testing regarding perioperative outcome. The observational studies do not provide valid evidence that preoperative testing is beneficial in healthy adults undergoing non-cardiac surgery. There is no evidence derived from high-quality studies that supports routine preoperative testing in healthy adults undergoing non-cardiac surgery. Testing according to pathological findings in a patient's medical history or physical examination seems justified, although the evidence is scarce. High-quality studies, especially large randomized controlled trials, are needed to explore the effectiveness of indicated preoperative testing. [ABSTRACT FROM AUTHOR]